<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>20-检测数据类型</title>
</head>
<body>
<script>
  let num = 10
  console.log(typeof num)
  let str = 'pink'
  console.log(typeof str)
  let str1 = '10'
  console.log(typeof str1)
  let flag = false
  console.log(typeof flag)
  let un
  console.log(typeof (un))
  let obj = null
  console.log(typeof obj)


  let num1 = prompt('请输入第一个数：')
  console.log(typeof num1)
</script>
</body>
</html>